Z8 Encore! MCU
The Z8 Encore! from ZiLOG is a high-speed 8-bit microcontroller that can be programmed in C or assembly. It has sixty I/O lines and is available with a UART, timers, and interrupt generators, all of which are extremely handy for MIDI use. It also offers a few features, listed below, that make it extremely well-suited for this application.
Also very cool is that the development software is absolutely free, and the entire evaluation kit (pictured below) costs only $40. It is essentially a board that holds the IC down and provides power and a place to access its I/O lines. It also includes a serial port, pushbutton, and some LEDs for debugging or showing off.
Features
FLASH program memory
The programming is done on a PC using the provided development software, and it is uploaded to FLASH memory, allowing it to remain on the chip indefinitely until it is reprogrammed. This is important for performance devices; failures can be corrected by "power cycling" the equipment. The MCU will reset itself and run its program if the power is interrupted. A power failure can be disastrous to a computer running Windows or MacOS.
An added advantage of the FLASH memory is that the Encore! can permanently store data such as patterns and patch settings, and recall them after being powered down for long periods. There is no need to bring a computer to the performance.
Small part count
The device pictured above is the Development Kit for the Encore! series. It contains a power supply and numerous I/O headers for prototyping use. However, the only components that are necessary to build a working system are the MCU itself and its clock crystal (the two large components near the center of the board). These can be assembled in an area of only 2 square inches, so the Encore! can be integrated into handheld projects or wearable devices. It requires only a few milliamps of power, so a pair of AA batteries can power it for hours.
Wireless I/O
The Encore! can communicate with IrDA devices (like a PDA or laptop) with a built-in controller. The development kit provides the IR transceiver pre-wired so that prototypes can immediately use wireless interfacing. This system does not have sufficient range to keep the device connected during a performance, but it allows data such as patches and patterns to be "uploaded" before or during a performance without plugging in cables. It also provides for some interesting creative possibilities.
High performance
Although it is a low power microcontroller, it does not compromise computing power for power efficiency. It has features that resemble microcomputer CPU designs, and runs at speeds of up to 20 MHz. Processing MIDI data puts only a light load on its processing core, allowing nearly all of its resources to be applied to creative interpretation of the performance data. Additionally, it has DMA (direct memory access) available for all of its on-chip peripherals, allowing things like MIDI I/O and timing to occur without putting any load at all on the processor. This is important, as the device must be able to interpret and react to the performance without adding a noticeable delay.
Challenges
The Z8 Encore! is not a ready-to-use system like Teleos's products, nor is it specially designed to work with musical data as is MAX/MSP. It is a true off-the-shelf microcontroller, and developing applications requires an understanding of MCU design that is beyond the scope of an arts course. While many of the actual programming challenges will be interesting exercises, the essence of this project is to turn the Encore! into a performance tool in a musical context. The true challenge is to make it as intuitive and playable as a musical instrument. Before this can begin, however, the basic architecture of a musical data processor must be constructed.
Another obstacle is the requirement for fabrication of the completed project. The finished device will require some support components, connectors, and a power supply, and the surface-mount Z8 device requires a custom-made circuit board. A durable and unobtrusive case will be required to protect the electronics from the rigors of stage performance. The small size of the development kit helps in this respect; the entire kit measures only about four inches square and requires only a single power supply. The initial prototype will most likely be constructed of the development kit with a few wires added. As an extra bonus, the development kit provides a prototyping area on an unused part of the PC board (shown at the top corner in the photo). Parts can be soldered directly onto the PC board and interfaced to the MCU chip without wires.
Encore! Compared to Other MCUs
PIC
The PIC family is comparable to the Encore!, offering many of the same on-chip peripherals and performance characteristics. In fact, there are hundreds of projects already published on the web involving MIDI PIC applications. However, I'm not an experienced PIC programmer, and the development kit necessary to program and "burn" C code onto a PIC is several hundred dollars. Encore! also has one major advantage over PIC: the device can be re-programmed and debugged without removing it from the project being developed. The PIC can be emulated in-circuit by special hardware, but the necessary hardware costs over $600.
BASIC Stamp
Performance-wise, the BASIC Stamp is nearly the same as the PIC (it is in fact a PIC with some custom programming and a serial port), so it is equally well suited to MIDI use. However, the cheapest Stamp is over $50, making "adventuresome" applications less appealing. The compiled BASIC used by the PIC also makes timing difficult; interrupts (described in the software section) are handled differently, and it is difficult to determine exactly how much time elapses between instructions. This makes real-time systems more challenging to develop because the user's program runs "on top of" the software that Parallax has placed on the PIC. In-circuit programming is also not available on the Stamp.
MSP430
Texas Instruments' product is the major competitor against Encore! It has nearly identical specifications and features. In-circuit debugging, FLASH memory, and a wealth of I/O and interfaces are all available. The development kit is relatively inexpensive ($50-$100), and the chip requires only a crystal and power supply to operate. I am a fan of the MSP430, but I have one big grudge against TI: The C compiler provided with the "evaluation kit" limits the size of the executable you can build to 4k. This is not a problem with devices that have only 4k of memory, but the '430 is available with up to 64k of memory, and they expect users to pay serious money for serious applications. People have been using GCC to avoid this limitation, but this is done at the expense of the in-circuit debugging. I have enough experience with programmming to survive under these conditions, but I can plug the Encore! in and use it without any limitations or special "hacks." I suspect that TI will eventually remove this limitation from their software to comete with ZiLOG, and they should anyway; it's not too smart to offer a MCU solution and then limit the applications that it can be used for.
Link: http://www.rpi.edu/~murphj4/icomp/z8e.html
The Z8 Encore! from ZiLOG is a high-speed 8-bit microcontroller that can be programmed in C or assembly. It has sixty I/O lines and is available with a UART, timers, and interrupt generators, all of which are extremely handy for MIDI use. It also offers a few features, listed below, that make it extremely well-suited for this application.
Also very cool is that the development software is absolutely free, and the entire evaluation kit (pictured below) costs only $40. It is essentially a board that holds the IC down and provides power and a place to access its I/O lines. It also includes a serial port, pushbutton, and some LEDs for debugging or showing off.
Features
FLASH program memory
The programming is done on a PC using the provided development software, and it is uploaded to FLASH memory, allowing it to remain on the chip indefinitely until it is reprogrammed. This is important for performance devices; failures can be corrected by "power cycling" the equipment. The MCU will reset itself and run its program if the power is interrupted. A power failure can be disastrous to a computer running Windows or MacOS.
An added advantage of the FLASH memory is that the Encore! can permanently store data such as patterns and patch settings, and recall them after being powered down for long periods. There is no need to bring a computer to the performance.
Small part count
The device pictured above is the Development Kit for the Encore! series. It contains a power supply and numerous I/O headers for prototyping use. However, the only components that are necessary to build a working system are the MCU itself and its clock crystal (the two large components near the center of the board). These can be assembled in an area of only 2 square inches, so the Encore! can be integrated into handheld projects or wearable devices. It requires only a few milliamps of power, so a pair of AA batteries can power it for hours.
Wireless I/O
The Encore! can communicate with IrDA devices (like a PDA or laptop) with a built-in controller. The development kit provides the IR transceiver pre-wired so that prototypes can immediately use wireless interfacing. This system does not have sufficient range to keep the device connected during a performance, but it allows data such as patches and patterns to be "uploaded" before or during a performance without plugging in cables. It also provides for some interesting creative possibilities.
High performance
Although it is a low power microcontroller, it does not compromise computing power for power efficiency. It has features that resemble microcomputer CPU designs, and runs at speeds of up to 20 MHz. Processing MIDI data puts only a light load on its processing core, allowing nearly all of its resources to be applied to creative interpretation of the performance data. Additionally, it has DMA (direct memory access) available for all of its on-chip peripherals, allowing things like MIDI I/O and timing to occur without putting any load at all on the processor. This is important, as the device must be able to interpret and react to the performance without adding a noticeable delay.
Challenges
The Z8 Encore! is not a ready-to-use system like Teleos's products, nor is it specially designed to work with musical data as is MAX/MSP. It is a true off-the-shelf microcontroller, and developing applications requires an understanding of MCU design that is beyond the scope of an arts course. While many of the actual programming challenges will be interesting exercises, the essence of this project is to turn the Encore! into a performance tool in a musical context. The true challenge is to make it as intuitive and playable as a musical instrument. Before this can begin, however, the basic architecture of a musical data processor must be constructed.
Another obstacle is the requirement for fabrication of the completed project. The finished device will require some support components, connectors, and a power supply, and the surface-mount Z8 device requires a custom-made circuit board. A durable and unobtrusive case will be required to protect the electronics from the rigors of stage performance. The small size of the development kit helps in this respect; the entire kit measures only about four inches square and requires only a single power supply. The initial prototype will most likely be constructed of the development kit with a few wires added. As an extra bonus, the development kit provides a prototyping area on an unused part of the PC board (shown at the top corner in the photo). Parts can be soldered directly onto the PC board and interfaced to the MCU chip without wires.
Encore! Compared to Other MCUs
PIC
The PIC family is comparable to the Encore!, offering many of the same on-chip peripherals and performance characteristics. In fact, there are hundreds of projects already published on the web involving MIDI PIC applications. However, I'm not an experienced PIC programmer, and the development kit necessary to program and "burn" C code onto a PIC is several hundred dollars. Encore! also has one major advantage over PIC: the device can be re-programmed and debugged without removing it from the project being developed. The PIC can be emulated in-circuit by special hardware, but the necessary hardware costs over $600.
BASIC Stamp
Performance-wise, the BASIC Stamp is nearly the same as the PIC (it is in fact a PIC with some custom programming and a serial port), so it is equally well suited to MIDI use. However, the cheapest Stamp is over $50, making "adventuresome" applications less appealing. The compiled BASIC used by the PIC also makes timing difficult; interrupts (described in the software section) are handled differently, and it is difficult to determine exactly how much time elapses between instructions. This makes real-time systems more challenging to develop because the user's program runs "on top of" the software that Parallax has placed on the PIC. In-circuit programming is also not available on the Stamp.
MSP430
Texas Instruments' product is the major competitor against Encore! It has nearly identical specifications and features. In-circuit debugging, FLASH memory, and a wealth of I/O and interfaces are all available. The development kit is relatively inexpensive ($50-$100), and the chip requires only a crystal and power supply to operate. I am a fan of the MSP430, but I have one big grudge against TI: The C compiler provided with the "evaluation kit" limits the size of the executable you can build to 4k. This is not a problem with devices that have only 4k of memory, but the '430 is available with up to 64k of memory, and they expect users to pay serious money for serious applications. People have been using GCC to avoid this limitation, but this is done at the expense of the in-circuit debugging. I have enough experience with programmming to survive under these conditions, but I can plug the Encore! in and use it without any limitations or special "hacks." I suspect that TI will eventually remove this limitation from their software to comete with ZiLOG, and they should anyway; it's not too smart to offer a MCU solution and then limit the applications that it can be used for.
Link: http://www.rpi.edu/~murphj4/icomp/z8e.html